The increasing number of network-connected mobile devices, as well as the increasingly data-intensive applications run on these devices, continue to tax mobile-network infrastructure. As network bandwidth limits are reached, inefficiencies in network architectures and implementations become more apparent. One such inefficiency occurs in scheduling the delivery of packets to and from mobile devices.
In a prior-art general-packet radio service (“GPRS”) system such as a universal mobile-telecommunication system (“UMTS”), a gateway GPRS support node (“GGSN”) links a packet-switched network, such as the Internet, to the GPRS network. A serving GPRS support node (“SGSN”) is disposed one level of hierarchy below the GGSN and delivers packets to and from radio-network controllers (“RNCs”) in its geographical area. Each RNC controls one or more base-transceiver stations (“NodeB” stations). In such deployments, the mobile network operates as a transport network and is thus unaware of, for example, user-level TCP/UDP/IP sessions and application protocols above TCP/UDP.
Buffering packets for a plurality of users and selecting specific user packets and scheduling them for delivery over Mobile-Wireless networks based on different criterion is common in Wireless Base Stations (for example NodeB in UMTS and eNodeB in LTE), and Base Station Controllers (RNC in UMTS Network). Some criterion for selecting user packets and allocation of RF channel resources have included, (1) a Round Robin where-in the competing user packets are selected in round-robin fashion to achieve fairness among users, (2) a Max C/I where users with high channel quality are selected first for maximizing the cell throughput, and (3) a Proportional Fair Scheduler (PFS) that attempts a compromise between achieving the maximum cell throughput and fairness, so as not to starve out users with poor RF channel conditions. Packet schedulers incorporating the above packet routing protocols are found in the UMTS/HSPA network, NodeB (Base Station in UMTS network). These schedulers operate on the packets already received or buffered in the corresponding network device, such as NodeB.
The sources of these packets, for example application servers, or client devices use TCP/UDP etc. protocols to transmit packets to the User devices, which get buffered in the transit Network devices, such as NodeB. The packet sources are unaware of the underlying packet transport, and any transit network congestion points such as a congested wireless sector. Closed loop transport protocols, such as TCP, attempt to optimize the packet delivery for a specific User/TCP session to maximize session throughput that the underlying transport could achieve so as to minimize packet drops within the network elements. In the prior art deployments, TCP/UDP etc. application protocols are end to end and do not terminate in RAN or other devices that are closer to the Wireless network. U.S. patent application Ser. No. 12/536,537 (Ref 1) proposes Content Caching/Proxy device in the Radio Access network that is application & content protocol aware.
FIG. 1 illustrates an example of a network 100 that includes a UMTS radio-access network (“RAN”), the packet core network (CN), and the Internet. A GGSN 102 within the CN sends and receives content from a server 104 over the Internet 106. The RAN operates only as a transport network, and application sessions are therefore terminated outside the RAN (in, e.g., the Internet 106). When a mobile device 108 moves from a first position 110 to a second position 112, it leaves the coverage area of a first base-transmitter station 114 and enters the coverage area of a second base-transmitter station 116. RNCs 118, 120 use an inter-RNC logical connection 122 in accordance with industry-standard protocols to hand over control-plane and user-plane sessions to the new RNC 120 and new base-transmitter station 116. The hand-over in the user plane happens at the transport level, and any packets lost en route to or from the first base-transmitter station 114 via the first RNC 118 are re-transmitted to the mobile device 108 at its new position 112 using the second RNC 120 and the second base-transmitter station 116 (or other, similar recovery operations are performed).
In other examples, the common point in the network between the first position 110 and the second position 112 may be further “downstream” (e.g., if the two base-transmitter stations 114, 116 are managed by a common RNC 118) or farther “upstream” (e.g., if a first SGSN 120 or GGSN 102 manages the first base-transmitter station 114 and a second, different SGSN or GGSN manages the second base-transmitter station 116). Although packets are dropped in the system 100 during a base-transmitter transfer in each case, the higher upstream the common point, the more packets will be dropped and the greater the inefficiency of the transfer.
Existing Third-Generation Partnership Project (“3GPP”) standards define different types of mobility and relocation operations when a mobile device moves from the coverage area of the first base-transmitter station 114 (e.g., a NodeB/RNC combination in an UMTS network or an eNodeB in a long-term evolution (“LTE”) network) to the second base-transmitter station 116. These operations include intra-NodeB handover, inter-NodeB handover, and inter-RNC handover between two RNCs connected to the same or different SGSNs. The mobility and handover scenarios include soft handover, softer handover, and hard handover. The handover and relocation procedures in the prior-art 3GPP standards operate at the packet-transport level and do not, for example, terminate TCP or UDP sessions.